A bipartisan “gang” of eight senators fired the opening salvo on immigration reform Monday, proposing a plan that offers immediate legal status for many of the more than 10 million undocumented US immigrants but delays their embarking on a path to citizenship until a raft of border security and immigration enforcement mechanisms are in place.

President Obama, who made sweeping immigration reform a key promise in his reelection campaign and won more than 70 percentof the Latino vote in November, is delivering a speech in Las Vegas Tuesday to announce the White House initiative on the issue. House Republicans, too, are expected to take up their own proposals.

All the activity indicates that broad-based immigration reform, which for years languished in the realm of political impossibility, may now be within Washington’s reach.

“Other bipartisan groups of senators have stood in the same spot before trumpeting similar proposals. But we believe this will be the year Congress finally gets it done,” said Sen. Charles Schumer (D) of New York.

“The politics of this issue have been turned upside down,” he said. “For the first time ever, there’s more political risk in opposing immigration reform than in supporting it.”

Majority leader Harry Reid (D) of Nevada pledged on the Senate floor Monday to do “everything in my power as majority leader to get a bill across the finish line.” Senator Schumer said the group hoped to have the legislation written by March, with the bill hitting the Senate floor sometime in the late spring or early summer.

Schumer said Mr. Obama, during a call with Schumer and Sen. Dick Durbin (D) of Illinois on Sunday, was “delighted” with the bipartisan framework.

The Senate plan borrows heavily from prior immigration reform proposals. It would revamp nearly all parts of the immigration system to fix what the group calls a process that is “insurmountably difficult” for many immigrants as it includes long backlogs for family and employment visas that help incentivize illegal immigration.

Under the plan, advanced graduates of American universities in the STEM (science, technology, engineering, and math) fields would receive special eligibility for green cards.

A federal employment verification system to discourage illegal workers would be introduced alongside a more flexible guest worker policy, including special provisions for agriculture workers and a broader reform that would allow businesses to hire more low-skilled workers when the economy is strong and fewer when it weakens.

But the project’s most novel – and thorny – elements lie in how it would deal with the millions of unauthorized residents already here, who will be required to register with the government if they want to become citizens. In order for these residents to take the next step, however, America’s borders will have to be deemed secure and the immigration laws enforced.

In putting the principles into legislative language by their target date in March, the senators will need to decide the necessary metrics or milestones to measure progress on border security and immigration enforcement.

Border security

The bipartisan road map calls for beefed up border patrols, including advanced technological assistance like unmanned aerial vehicles, and a system that tracks when visitors enter and exit the country, among other measures.

The plan also calls for a commission of governors, attorneys general, and community leaders from Southern border states to offer their recommendation when the border has actually become secured.

But that proposal raises questions of how the commission will be constructed, whether it alone will determine when border security has been achieved, and which metrics will be used to determine when the bill’s requirements are met.

“In theory, I think [the border commission] sounds fine, but in actuality the border is never 100 percent secure,” says Susan Cohen, chair of the Immigration Practice at law firm Mintz Levin in Boston. “But it’s much more secure now than it used to be, and I think that it’s not unrealistic to think we could get to a point where some commission could certify it as secure for that purpose.”

It’s an important concern, because whichever mix of policy prescriptions ends up in the final bill, the outline calls for all of the pieces of the enforcement puzzle to be assembled before a single undocumented immigrant receives a green card.

Long path to citizenship

Should lawmakers solve that problem, then they will take on the politically sensitive task of determining what counts as the “tough, fair, and practical roadmap” to citizenship for the vast majority of America’s undocumented. The initial proposal spells out a lengthy path.

(Agriculture workers and young undocumented immigrants known as “DREAMers” would go through a separate, less arduous, process to achieve citizenship, however.)

The bipartisan proposal would require undocumented residents first to register with the government. Pending a background check and financial transactions including back taxes and the paying of a fine, the individuals would receive legal residency in the US that allows them to work and obtain drivers licenses.

Then, once the border security and enforcement measures are in place, those with legal status would have to pass an additional background check, learn English and civics, and provide proof of their work history in the US, among other requirements, in order to take a place in line for legal permanent residency behind all other applicants for green cards at the time the legislation is enacted.

The bipartisan group is “creating a road to citizenship and making sure undocumented immigrants are starting at the back of the road,” says Ali Noorani, head of the American Immigration Forum. “They want to make sure that folks who are in the process, that path remains free of obstruction for them.”

But how long will that process take? That remains to be hashed out, an aide to one Democratic senator involved in the group said Monday.

According to immigration reform principals enunciated by Obama in 2011, undocumented individuals would have to wait eight years before obtaining legal permanent residence and then another five years more before being eligible for citizenship.

That timeline could be “aggressive,” says Ms. Cohen of Mintz Levin, because current backlogs for some green cards stretch more than a decade, and it remains to be seen what types of changes forthcoming legislation would offer to shorten wait times for current applicants.

Opposition to proposal

But for many opponents of past immigration fixes, even nearly two decades of waiting appeared too much like amnesty.

“In the race to out-amnesty Obama, the Gang of Eight today rehashed the failed amnesty plan from six years ago,” said Rosemary Jenks, director of government affairs for Numbers USA, an advocacy group that fights for lower immigration levels, calling the plan little more than “Amnesty 2.0.”

“When you legalize those who are in the country illegally, it costs taxpayers millions of dollars, costs American workers thousands of jobs, and encourages more illegal immigration,” Representative Smith said in a statement. “By granting amnesty, the Senate proposal actually compounds the problem by encouraging more illegal immigration.”

But even in the face of opposition, Senate lawmakers and a wide array of interest groups from the conservative-leaning Chamber of Commerce to the liberal AFL-CIO expressed optimism that this time would, in fact, be different.

The growing clout of Latino and Asian voters, those confident of reform say, will provide the final political push necessary to get legislation to the president’s desk before year’s end.

“Elections,” said Senator McCain, a veteran of immigration political wars, in a one-word explanation of why the current gang would succeed where others had failed. “Elections. The Republican Party is losing the support of our Hispanic citizens.... This is a preeminent issue for those citizens.”